Coutts will not be disclosing it publicly if they have concerns regarding where the funds came from . That would be tipping off which is illegal.
What you see in the media is information obtained from CRM data.
Banks do not store AML information where it can be requested by the account holders. If your bank think you're money laundering and they close your account, you can submit a subject access request but it will not include reports of suspicious activity as that would be tipping you off.
The bank is confident with their decision for the flvery simple fact that they have not asked him to go bank with them again.
FCA has very clear guidelines on what is permissable and what is not.
Ultimately he is throwing a tantrum because he no longer has the benefits that come with being a private client.
Coutts probably wanted him gone for a while, he repaid his mortgage, doesn't qualify any further and they took the opportunity to get rid off him.
As much as you may not like it banks are actual businesses and they have the right to turn you away for nonessential products such as private banking.
NatWest has offered him the essential option which he is entitled to which is a normal bank account.